Present day strike-slip deformation within the southern part of the İzmir-Balıkesir Transfer Zone based on GNSS data and implications for seismic hazard assessment in western Anatolia

Abstract

Here, we present a combined analysis of GNSS-derived strain rate maps in accordance with recent seismicity to reveal that the N-S extension is accommodated primarily by strike-slip faulting of the İzmir Balıkesir Transfer Zone (İBTZ) where a counter clockwise rotation (approx. 25-100º/Myr) along vertical axis is dominant. Our results indicate that strike-slip segments within the İBTZ show variable transport sense and amount of slip along them and they connect by hard linkage relay ramps with the dip to oblique slip normal faults. According to the strain map, Karaburun Peninsula has the largest strain rates of 137 ns/yr extension (NE-SW) and 126 ns/yr (NW-SE) compression. To the south the largest strain areas begin to shrink where the NW-trending sinistral Riedel fault is located. The smallest strains in the region are measured on the NEtrending Tuzla Fault compatible with right lateral component. Based on this, the northern part of the Karaburun Peninsula has the shortest recurrence period in the 3 region. The geodetic earthquake recurrence periods throughout the region as 800 yr for magnitudes 7 and above and 70 yr for magnitudes between 6 and 7. The period was calculated 30 years for M>5.5 (with 99% probability) and 100 years for M> 6 (with 95% probability). These are in consistent with geodetic earthquake recurrence periods (25-30 years for M> 5.5 and 80-100 years for M> 6). This result shows that the seismic hazard sources in the region have increased the earthquake risk that may caused loss of life and property in near future.

Active Tectonics of Gülbahçe Fault Zone (GBFZ) by Using Geomorphic Indices, İzmir Province, Western Anatolia, Turkey

“…Because of this situation and annual uplift rate of basin, it may indicate that the Karaburun peninsula may break away from Anatolia in the future and then turn into an island like Chios, located in the west. Splaying of the fault in the north and related subsidence around Gülbahçe bay can be explained by the counter anti-clockwise rotational movement of the Karaburun peninsula block which was also stated by geodetic and paleomagnetic studies (Aktuğ and Kılıçoğlu 2006, Uzel et al 2013, Eyubagil et al 2021. Besides this, obtained results show that the western splay of GBFZ is more affected on the drainage basins with a high relative tectonic activity.…”

“…This seismically active dextral strike-slip fault zone (Bozkurt and Sözbilir 2006) forms a boundary between Karaburun Peninsula and Urla block, faraway 45 km west of İzmir city from the east (Emre et al 2005), extending for ~24 km on land and ~46 km under the sea (Emre et al 2016, Ocakoğlu et al 2005. With respect to GPS studies, the Karaburun Peninsula turn anti-clockwise due to dextral strikeslip nature of the N-S trending GBFZ (McClusky et al 2000, Nyst and Thatcher 2004, Reilinger et al 2006, Eyubagil et al 2021. Although, GBFZ have been identified and documented as an active fault in active fault database of Turkey by Emre et al (2016); there is not detailed geomorphic studies about its tectonic activity.…”

GPS derived finite source mechanism of the 30 October 2020 Samos earthquake, Mw = 6.9, in the Aegean extensional region

“…62 GNSS sites covering the region were used (Aktuğ and Kılıçoğlu 2006;Aktuğ et. al., 2009;Özener et al, 2013;Çırmık et al, 2017a;Eyübagil et al, 2021 Min. 8-h with 30s interval GNSS measurement was carried out between 5th and 8th of November 2020 at campaign type sites to calculate post-earthquake coordinates Figure 4).…”

Seismic Activity of the Manisa Fault Zone in Western Turkey Constrained by Cosmogenic 36Cl Dating

“…IBTZ was demonstrated to be a deep crustal transform fault zone during Late Cretaceous, which acted as a transtensional transfer zone in the Neogene period ( [43][44][45]). Recent seismicity with focal mechanism, Global Navigation Satellite System (GNSS) measurements and several geological studies indicate that IBTZ is undergoing an E-W shortening as well as N-S extension (e.g., [43][44][46][47][48][49]). Here, recent investigations confirm a very close connection between the normal surface ruptures and large magnitude 6 or higher earthquakes (e.g., [33][34][35][50][51][52]).…”